There are numerous techniques available for reducing the nicotine delivery from tobacco smoke. However, most of these techniques also result in the reduction of tar delivery. For various reasons, such as achieving pleasant taste from tobacco smoke, it is desirable to be able to selectively reduce tar or nicotine delivery, i.e., to reduce tar or nicotine delivery relative to each other. The cigarette wrapper of the present invention provides means for selectively reducing nicotine delivery.
Tobacco foils prepared from cellulose derivative binders filled with finely ground tobacco are well known in the art. For example, U.S. Pat. Nos. 1,716,250; 2,485,670; 2,598,680; 2,706,695; 2,797,689; 2,830,597; 2,893,400; 2,897,103; 2,927,588; 2,955,601; 3,062,688; 3,288,148; and 3,43,546 all disclose tobacco foils prepared from finely ground tobacco dispersed in a matrix of a cellulosic binder. Typical binders include cellulose esters or cellulose ethers such as methyl cellulose, carboxymethyl cellulose, or cellulose acetate. Generally, such tobacco foils are disclosed as useful as cigar wrappers. However, foils prepared from cellulose derivative binders filled with ground tobacco have also been proposed as cigarette wrappers. See German Offen. 2,008,150.
None of the patents referred to above pertaining to tobacco filled foils suggests substituting a finely ground paper filler for the finely ground tobacco filler. Certain of the above listed patents (e.g., German Offen. 2,008,150) disclose that the use of the tobacco foils as cigarette wrappers effects a reduction in tar and nicotine delivery. However, none of the prior art recognizes that such wrappers would be effective to selectively reduce nicotine delivery, i.e., decrease the nicotine delivery to a greater degree than the tar delivery, thereby increasing the tar/nicotine ratio. Furthermore, tobacco filled thermoplastic foils have not proven successful as cigarette wrappers. Tobacco filled foils impart a heavy, sour-sweet, or "stemmy" off-taste to cigarette tobacco smoke.
Inclusion of potassium nitrate in cigarette wrappers is also known in the prior art. U.S. Pat. No. 2,171,986 discloses adding potassium nitrate to conventional paper cigarette wrappers, in combination with certain other nitrogen containing compounds, to produce a mildly alkaline smoke. However, as noted in the patent, the inclusion of sufficient amounts of potassium nitrate, in the absence of other nitrogen containing compounds, to obtain the desired mildly alkaline smoke adversely affects the ash and burning qualities of the paper. According to the disclosure of this patent, cigarette paper ordinarily produces an acid smoke, while an alkaline smoke is supposedly less irritating.
A number of other patents, such as U.S. Pat. Nos. 1,983,530 and 2,091,598 disclose the addition of potassium nitrate, as a combustion rate accelerator, to cigarette wrappers prepared from regenerated cellulose films. Neither of these patents suggest that KNO.sub.3 has any effect on tar or nicotine delivery.
U.S. Pat. No. 3,699,972 discloses the use of combustion-accelerating agents, such as potassium nitrate, to treat preselected areas of cigarette wrappers. The combustion-accelerating agents cause the treated area of a cigarette wrapper to burn more rapidly than untreated surrounding areas so that increased air flow is obtained through the rapid burning areas. While such wrappers are effective to reduce tar and nicotine deliveries, such wrappers do not result in selective nicotine delivery reduction.
The porous thermoplastic wrappers of the present invention provide a method of selectively reducing the nicotine delivery from normal cigarette tobacco blends. In addition, unlike tobacco filled wrappers, the thermoplastic wrappers of the present invention do not impart a heavy, sour-sweet, or "stemmy" off-taste to cigarette tobacco smoke.
In the present specification, unless otherwise specified, all references to percentages of the various ingredients are by weight, based on the total weight of the composition.